Note: Descriptions are shown in the official language in which they were submitted.
GECAN3093
Field of the Invention
The present invention is directed to an apparatus for use in
a nuclear reactor and, in particular, an apparatus for axial alignment
within a fuel channel end fitting of a nuclear reactor.
Backctround of the Invention
The fuel channel end fitting of a nuclear reactor is the
communication port between the fuel channel and the outside. Over
time, the movement of equipment and fuel bundles within and around
the end fitting causes the end fitting to wear resulting in deviations in
the end fitting dimensions. The end fitting must be reworked; especially
at the sealing surfiaces, to maintain its integrity and to ensure proper
sealing of the fuel channels. Reworking processes such as milling or
lapping must be carried out to precise dimensions. For example, the E-
face seal of the end fitting creates a metal to metal seal with the fuel
channel closure. Lapping of this seal is occasionally required to
maintain the integrity of the seal. The lapping process must be carefully
controlled to ensure that the seal is lapped to be exactly concentric
relative to the axis of the end fitting. Further, the seal must be lapped
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evenly over its entire surface. Previously, reworking processes were
carried out using manually operated tools positioned within the end
flitting in axial alignment with the end fitting. Axial alignment was
accomplished by means of manual measurements and trial and error.
Understandably, the accuracy of the alignment was not always perfect
and this sometimes led to irreparable damage of the end fitting. To
avoid damage to the end fitting during reworking, it is necessary that
any apparatus used in association with the end fitting is initially aligned
with the axis of the end fitting and that this initial alignment is
maintained during any reworking operation.
Summary of the Invention
In accordance with a broad aspect of the present invention,
there is provided an apparatus for axial alignment within a fuel channel
end fitting ofi a nuclear reactor, the apparatus comprising:
a shaft comprising an inward end for insertion into the fuel
channel and a smaller outboard end opposite the inward end, the
inward end comprising a predetermined taper, the taper being
positioned to taper toward the outboard end of the shaft; and,
a mating expanding collet arrangement comprising a
plurality of collet segments supported on the taper and arranged
concentrically about the shaft, each collet segment adapted to move
radially outwardly from the shaft when the taper is inserted into the
collet;
wherein when the inward end of the shaft is inserted into the
fuel channel, the collet arrangement is forced radially outwardly to bind
with the inner surface of the fuel channel such that the shaft is in axial
alignment within the fuel channel end fitting.
In accordance with a further aspect of the present invention,
there is provided an apparatus for supporting a lapping tool in position
relative to the axis of a fuel channel end fitting of a nuclear reactor, the
apparatus comprising:
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positioned to taper toward the outboard end and a threaded portion,
adjacent the taper;
a mating expanding collet arrangement comprising a
plurality of collet segments supported on the taper and arranged
concentrically about the shaft, each collet segment adapted to move
radially outwardly from the shaft when the taper is inserted into the
collet;
a collet nut threadingly engaged on the threaded portion of
the shaft and moveable along the shaft to act against the collet
segments and insert the taper into the collet arrangement; and,
wherein the shaft is adapted to carry the lapping tool; and,
wherein when the inward end of the shaft is inserted into the
fuel channel, the collet nut is advanced along the shaft to force the
collet arrangement radially outwardly to bind with the inner surface of
the fuel channel such that lapping tool is in position relative to the axis
of the fuel channel end fitting.
Brief Description of the Drawinas
For a better understanding of the present invention
reference is made by way of example to the following diagrammatic
drawings, in which:
Figure 1 is an exploded perspective view of the apparatus of
the present invention aligned to enter a fuel channel end fitting; and,
Figure 2 is a cross section elevational view through an end
fitting having the lapping tool of the present invention disposed therein.
Detailed Description of the preferred Embodiment
Referring to Fig. 1, there is shown the apparatus 10 of the
present invention aligned for entry into a fuel channel end fitting 20 the
remote end of which enters the fuel pressure channel (not shown). An
exemplary end fitting contains a number of surfaces which require
reworking throughout the life of the structure. Three such surtaces are
the radial seal 21 of the seal ring, the flat face seal 22 of the seal ring
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and the E-face seal 23. Various tools are used for the reworking of
these surfaces. Alignment of the reworking tool with the central axis,
indicated at 25, of the end fitting 20 allows precise reworking of the
concentric sealing surfaces 21, 22 and 23. The apparatus 10 of the
present invention allows precise axial alignment of a tool within a fuel
channel end fitting.
Fig. 1 shows the apparatus 10 exploded into its component
parts. The apparatus comprises a tapered shaft 30 and a mating
expanding collet 40. Shaft 30 has an inward end 32 for insertion into
the end fitting 20 and a smaller outboard end 34 opposite the end 32.
End 32 of the shaft 30 is positioned to taper toward the outboard end 34
of the shaft 30. The taper 36 is made to mate with a collet arrangement
40. As is known in the art, the collet arrangement 40 comprises a
plurality of collet segments 42 which are arranged concentrically about
the shaft 30 and are adapted to move radially outwardly when the taper
36 is inserted into collet 40.
Apparatus 10 of the present invention maintains axial ~.
alignment within the fuel channel 20 in a well known manner, readily
understood by those skilled in the art. When the inward end 32 of the
shaft 30 is inserted into the fuel channel end fitting 20, the collet
arrangement 40 is forced radially outwardly along the taper 36 to bind
with the inner surface 60 of the end fitting 20. This forces the shaft 30
of the apparatus 10 into axial alignment with the end fitting 20.
The collet arrangement 40 is comprised of a plurality of
collet segments 42. The number of segments 42 required for the
function of the apparatus is three or more. In the most simplified and
therefor most preferred apparatus, the number of segments 42 is three,
as shown in Fig. 1. The collet segments 42 may be maintained on the
shaft 30 by any suitable means. For example, as shown in Fig. 1, by a
pair of 0-rings 45, 46 resting in a pair of grooves 47, 48 encircling the
collet arrangement 40.
The inner surface 50 of each collet segment 42 is adapted
to move smoothly over the taper 36. Preferably, the inner surface 50 of
each collet segment 42 is adapted to have contacting surfaces 52 only
at the ends to reduce the frictional forces and thereby allow enhanced
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movement of the segments 42 over the taper surface 36. This feature is
best seen in cross section as shown in Fig. 2.
Referring again to Fig. 1, the outer surface of the collet
segments 42 are adapted to bind with the inner surface 60 of the end
fitting 20. To provide stability of the shaft 30 along its length when in
axial alignment within the end fitting 20, it is understood that each
segment 42 must bind with the inner surface 60 at more than one point.
Debris within the end fitting may come between the binding surface and
the inner surface of the end fitting and cause improper binding. To
avoid improper binding, the entire outer surface of each segment 42
preferably does not bind with the inner surface 60 of the end fitting 20
but rather, each segment 42 binds simultaneously at at least two
binding surfaces 65 along its outer surface. In the most preferred
embodiment, the two binding surfaces 65 are positioned at apposite
ends of each segment 42 as shown. This arrangement of binding
surtaces 65 is shown in Fig. 1 also having the O-ring grooves 47, 48
extending thereacross. Binding surfaces 65 are preferably comprised of
a curved face having a radius in agreement with that of the inner
surface 60 of the end fitting 20 to allow the apparatus 10 to be more
securely bound.
The taper 36 may be inserted into the collet 40 by any
suitable means. In a preferred embodiment, a threaded portion 70 is
worked onto the shaft 30 adjacent the taper 36 to threadingly engage a
collet nut 80. As best seen in Fig. 2, an end portion 82 of each segment
42 extends over the threaded portion 70. Collet nut 80 is tightened
along the threaded portion 70 into contact with the segments 42.
Further tightening of the nut 80 forces the taper 36 to be inserted into
the collet 40 causing the collet 40 to expand radially outwardly from the
shaft 30 until the binding surfaces 65 of the segments 42 bind with the
inner surface 60 of the end fitting 20. The collet nut 80 acts to lock the
collet arrangement 40 in the radially extended position until the nut 80 is
loosened to remove the force exerted by the nut 80. The nut 80 may be
adapted to be in direct engagement with the collet segments 42. As
shown in Fig. 2, in a preferred embodiment a flange 84 extends from the
nut 80 toward the segments 42. A mating flange 86 extends out from
each of the collet segments 42 toward the nut and is engaged by the nut ,
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flange 84. The flanges 84, 86 provide that any movement by the nut 80
along the threaded portion 70 is directly translated to the collet
segments 42.
The apparatus 10 as described hereinabove allows axial
alignment of the shaft 30 of the apparatus 10 within the end fitting 20.
The shaft 30 of the apparatus 10 may be adapted to support a tool and
thereby convey axial alignment to the tool. The various tools may be
positioned in appropriate places on the apparatus to allow work on the
end fitting to be carried out. In an exemplary embodiment, as shown in
Fig. 2, the shaft 30 is adapted to support a set of lapping tools 90, 92
positioned to refinish the radial seal 21 and/or the flat face seal 22 of
the end fitting 20. In this embodiment, the shaft 30 is hollowed along
the length of its axis (shown coaxial with the axis 25 of the end fitting
20) to accommodate a lap arbor 95 extending beyond each end 32, 34
of the shaft 30. The lapping tools 90, 92 are supported by the arbor 95
adjacent the inward end 32 of the shaft 30. An operator (not shown) is
able to control the lapping tools 90, 92 by appropriate means such as a
handle 97 attached to the arbor 95 adjacent the outboard end 34 of the
shaft 30. To rework the sealing surfaces 21, 22, the end of the shaft 30
supporting the lapping tools 90, 92 is placed in the end fitting 20 and is
adjusted into axial alignment within the end fitting 20 by means of
tightening the collet nut 80 to force the collet segments 42 into binding
engagement with the inner surface 60 of the end fitting 20. This axially
aligns the lap arbor 95 with the end fitting and positions the lapping
toots 90, 92 orthogonal to the axis 25 of the end fitting 20. To begin the
lapping procedure, the tools 90, 92 are advanced by the arbor 95 to be
in contact with the seal to be reworked. It is to be understood that other
tool arrangements may be used with the aligning apparatus of the
present invention. For example, Tapping tools may be positioned on the
outer end of the shaft to rework the E-face 23 seal of the end fitting.
